Transistor test set having input currents related to 10n/2



y 30,1967 A. B. BERESKIN 3,323,060

TRANSISTOR TEST SET HAVING INPUT CURRENTS RELATED TO 10 Original FiledJune 12, 1962 INVENTOR ALEXANDER B. Beeesmu ATTORNEKS United StatesPatent 3,323,060 TRANSISTOR TEST SET HAVING INPUT CURREN'IS RELATED TO10 Alexander B. Bereskin, 452 Riddle Road, Cincinnati, Ohio 45231Continuation of application Ser. No. 201,939, June 12, 1962. Thisapplication May 6, 1966, Ser. No. 548,335 3 Claims. (Cl. 324-158) Thisis a continuation of application Ser. No. 201,939 filed June 12, 1962.

The present invention relates generally to transistor testing equipmentand more particularly to a transistor test set for measuring dynamicand/ or D.C. current amplification factors with the use of a directreading meter.

The need presently exists for transistor test equipment wherein currentamplification factors, and particularly the Beta amplification factors,may be obtained without calculations of any nature. In prior test sets,the D.C. amplification factor is generally obtained by insertion of aseparate meter in the transistor input and output circuits. The currentflowing in these circuit is read and the ratio between them computed toascertain the transistor D.C. current amplification factor. To determinethe dynamic amplification factor, an A.C. current is inserted in theinput and the resulting A.C. output current is read. The ratio betweenthe A.C. output and input currents is then computed to obtain thedesired result. As an alternative, bridge circuits have been used tonull the resulting A.C. output current against the A.C. input current,with dynamic Beta being computed from the bridge settings. Theseapproaches are extremely time consuming, thus eX- pensive, and lead tomany errors due to calculation mistakes.

The present invention provides a transistor test set in which thecurrent amplification factors may be read directly from a single currentreading meter. In a system for the measurement of dynamic and D.C. Betaamplification factors, the meter is connected in the transistorcollector-emitter circuit and accurately controlled currents are appliedto the base. The currents are controlled by variable resistances whichare fed by a constant voltage source. In a preferred embodiment, themeter is a 0-100 microampere movement and includes a pair of scales, onehaving a range of 10 (0-100) and the other a range of 10 (0-316). Thismeter is furnished with a multiplicity of shunts which are decimallyrelated to the two scales so that direct Beta readings over very wideranges for many types of transistors are possible. The input currentsare limited to values which are decimal multiples of where n is anypositive integer, except that provisions are also made for doubling thevalues of the input currents. With this choice of meter scales andshunts, and restricted values of input currents, for every input currentselected there is a numerical value on the meter scale which isdecimally related to the current amplification factor, except that whenthe input current has been doubled the numerical value on the scale istwice the value decimally related to the current amplification factor.

To measure the dynamic Beta factor, a balancing circuit is connected tothe meter. A D.C. current having a value related to 10 is applied to thetransistor base circuit and the meter reading is set to zero by thebalancing circuit. The base current is now increased by an incrementrelated to 10 Virtually all of the increased collector current flowsthrough the meter circuit so that a direct indication of the dynamicamplification factor is obtainable.

As an added feature, the flexibility of the present system is increased,if necessary, by doubling the magnitude of the input current. This isaccomplished by doubling the input voltage which supplies the basecurrent through the current controlling resistors. The feature ofincreasing the base current by a factor of two provides the same numberof test points, and approximately the same values of currents, as wouldbe available if the input current were controlled according to thefactor of 10 but does so with only one half as many input currentcontrolling circuits. By using a voltage doubling arrangement, thenecessity for a complex resistor control circuit and switchingarrangement is avoided. To ascertain amplification factor with thelarger input voltage applied to the system, it is merely necessary tohalve the meter reading, a simple mental calculation.

It is accordingly an object of the present invention to provide a newand improved transistor test set by which current amplification factormay be easily determined.

It is another object of the present invention to provide a transistortest set wherein both dynamic and D.C. current amplification factors maybe directly read from a single meter.

A further object of the present invention is to provide a transistortest set wherein currents related to 10 are applied to the input circuitof a transistor and a current measuring meter having a first full scalereading of 10 where 11 is an even integer, and a second full scalereading of 10 where n is an odd integer, is provided.

An additional object is to provide a transistor test set for determiningcurrent amplification factors wherein the input current is selectivelyrelated to 10 or approximately to 10 the selection being achieved bymerely doubling the supply voltage for the input current.

Yet another object of the present invention is to provide an accuratetransistor test set for ascertaining dynamic and D.C. Beta currentamplification factors with minimum effort on the part of an operator;minimum number of components; and hence minimum initial and operatingexpenses.

The above and still further objects, features and advantages of thepresent invention will become apparent upon consideration of thefollowing detailed description of one specific embodiment thereof,especially when taken in conjunction with the accompanying drawings,wherein:

FIGURE 1 is a circuit diagram of a preferred embodiment of theinvention; and

FIGURE 2 is a diagram of a meter dial used in the circuit of FIGURE 1.

Reference is now made to FIGURE 1 of the drawings 7 which discloses NPNtransistor 11, the transistor to be tested for D.C. and dynamic Betaamplification factors. Transistor 11, connected in the common emittermode, has its emitter 12 connected to ground 13, its collector 14connected to switch contact 15, and its base 16 connected to lead 17.

Connected to lead 17 are ten different switch contacts 21-30, which areadapted to engage switch armatures 31-40, respectively. Armatures 31-40normally are spring biased on contacts 41-50, respectively, which areconnected to ground 13. Connected to armatures 31-40 are ten inputcurrent controlresistors 51-60 which are all connected to switcharmature 61 which normally couples the positive terminal of D.C. powersupply 62 to the resistors via contact 63. Armature 61 can be switchedto engage contact 64 and thereby double the voltage to resistors 51-60by coupling the series connected supplies 62 and 65 in the circuit.

In a preferred embodiment of the invention, each of the supplies 62 and65 is a 47.2 volt D.C. source and resistors 51-60 are 47 megohms, 15megohms, 4.7 megohms, 1.5 megohms, 470 kilohms, kilohms, 47 kilohms, 15kil- 3 ohms, 4.7 kilohms and 1.5 kilohms, respectively. Thus, thecurrents flowing through resistors 51-60 are 1.0 microampere, 3.16microamperes, 10 microamperes, 31.6 microamperes, 100 microamperes,0.316 milliampere, 1.00 mil- 4 The manner in which the present circuitis utilized to ascertain D.C. Beta factor, h will now be described.Selector switch 71 is positioned at the desired or expected range, and asingle one of switches 31-40 is activated to liampere, 3.16milliamperes, 10 milliamperes and 31.6 5 engage its respective contact21-30 to cause the desired milliamperes, respectively. These currentsare equal to value of collector current to flow. To determine the propermicroamperes, where n is any integer between 0 and Beta range thefollowing table of Beta range as a function 9. Positioning of any of thearmatures 31 to 40 on conof base input resistance and full scaledeflection of meter tacts 21-30 results in an input current to base 16corre- 93 is consulated:

TABLE 1 Beta Range Collector Current Range, ma.

.100 .316 1. 00 3.16 10. 0 31. 6 100 316 1, 000 .316 1. 00 3.16 10.0 31.6 100 316 1,000 3,160 1. 00 3.16 10.0 31. 6 100 316 1,000 3.1 10.0 31. 6100 316 1,000 160 M. 4. 7 M. 1.5 M. 470 K. 150 47 K. 15 K. 4. 7 K 1 5 K.

sponding with that through the associated resistance. By positioningarmature 61 on contact 64, the current through each of the resistors51-60 is doubled and results in control of the input current as afunction of approximately lO By utilizing this arrangement optimumselection of input currents in achieved with a minimum number ofcomponents.

Connected in the collector circuit of transistor 11 is switch 71,including ganged armatures 15 and 72 which are adapted to engagecontacts 73 and 74, respectively. Each of the ten pairs of contacts 73and 74 is connected directly together by strapping 75 so that the meteris protected from carrying full collector current in case of defectiveswitch contacts. Connected to nine of the contacts 74 are resistors81-89, the other contact being open circuited. Resistors 81-89 have oneterminal connected to the positive terminal of DC. supply 91, the otherterminal of which is grounded.

Connected between the positive terminal of supply 91 and armature 72 isa series circuit including current limit ing resistor 92 and DC.microammeter 93. Microammeter 93 preferably has a full scale deflectionof 100 microamps and include two scales. As illustrated in FIGURE 2,microammeter 93 includes needle 90 and scales 94 and 95 which extendbetween 0-100 and 0-316, respectively.

To provide the proper calibration for meter 93, the meter and resistor92 have a total series resistance of 1.5 kilohms. Meter shuntingresistors 81-89 have values of 695 ohms, 167 ohms, 49 ohms, 15.1 ohms,4.76 ohms, 1.50 ohms, 0.475 ohm, 0.150 ohm, and 0.0475 ohm, respectivelywhich result in full scale deflections of 0.316, 1.00, 3.16, 10.0, 31.6,100, 316, 1000, and 3160 milliameres for the different resistancevalues. Of course, when armatures 15 and 72 engage the open circuit setof contacts 73 and 74, the full scale meter deflecton is 0.100milliamps.

For dynamic Beta measurements, armature 94 is moved from open contact 95to contact 96 so that the balancing circuit 97 is connected betweenmeter 93 and resistor 92. Circuit 97 includes a balancing variableresistance 98, which has one of its terminals connected to armature 94;its other terminal and slider 100 are connected to current limitingresistor 99. The impedance of balancing circuit 97 is sufficiently highso that substantially all of the incremental collector current will flowthrough meter 93 once balance is achieved.

To measure I the transistor collector-emitter current with an opencircuit base electrode, switch 71 is set to the position required toread the current through meter 93 and each of the switches 31-40 ismaintained in its normal position, engaging contacts 41-50. With theselection of collector currents available with switches 71, it is.possible to measure characteristics of transistors ranging between lowsignal silicon and power germanium. Of course for testing of even higherpower elements, additional taps may be included in switch 71.

The column associated with each of the base resistors 51-60 ispreferably positioned in proximity with its respective switch activatingbutton.

To illustrate the manner in which the table is utilized, it is assumedthat armature 35 is brought into engagement with contact 25, switch 71is connected to resistor 83, and needle points to 50 on scale 94 and 158on scale 95. The connection of switch 71 with resistor 83 produces afull scale current of 3.16 milliamperes in meter 93. The intersection of470K and 3.16 is consulted and Beta range is read from the left columnas 31.6. Since needle 90 reads 158 on scale 95, the DC. Beta factor isthen read as 15.8. As a further illustration it is assumed the 4.7megohm resistor 53 is connected in the base circuit, switch 71 isconnected to resistor 82 which provides for a full scale reading of 1.00milliampere and needle 90 is deflected so that readings of 25 and 79 aremade on scales 94 and 95, respectively. The intersection of 4.7M and1.00 is found on the table to correspond with a Beta range of 100. TheDC. Beta amplification is thus found to be 25.

If it is desired to determine the amplification factor at intermediatebase current values, the input current is doubled by engaging switch 61with contact 64 so that supply 65 is introduced into the circuit. Thisresults in a deflection of needle 90 over what it normally would be forthe corresponding input or base resistance. The meter reading is thusdivided by two to ascertain Beta with great simplicity.

To measure dynamic Beta factor, h single pole, double throw switch 94 isoperated to engage contact 96. While maintaining the base current at thesame value as it was during measurement of h the slider of rheostat 98is rotated to produce a null reading on meter 93. The base current isincreased by switching in parallel a higher resistance into the basecircuit while maintaining the original resistance in the circuit. Thisresults in additional collector current and a deflection of needle 90.Substantially all of the increased current flows through the shuntresistors 81-89 of meter 93 and through meter 93 and resistor 92 due tothe relatively high impedance of the balancing circuit so that anaccurate indication of the current increment is obtained from the meterreading. The deflection of meter 93 is an accurate measurement of thedynamic Beta factor. The above table is utilized by consulting the baseresistance column associated with the additional resistance. Otherwise,the table is utilized to determine dynamic Beta factor in the samemanner as it is used for DC. Beta.

While I have described and illustrated one specific embodiment of myinvention, it will be clear that variations of the details ofconstruction which are specifically illustrated and described may beresorted to without departing from the true spirit and scope of theinvention as defined in the appended claims.

I claim:

1. In a circuit for measuring DC. and dynamic current amplificationfactor of a transistor under test, and collector-emitter current withbase open, the combination comprising means for connecting saidtransistor in common emitter operational mode in said circuit; firstmeans for supplying direct current; a first plurality of electricalresistance elements; switch means for selectively applying current fromsaid first direct current supply means to the base electrode of saidtransistor via any one or more of said resistance elements to supplyincrementally variable base current to said transistor; said first meansfor supplying direct current including a first constant voltage sourceand a second constant voltage source, said voltage sources being of thesame voltage values, and switch means for selectively connecting one ofsaid constant voltage sources or both of said constant voltage sourcesin series to provide said current; said first plurality of resistanceelements having resistance Values selected to restrict incrementalvariation of said base current to current values within the set currentunits, where n is an integer, 06 n 9;

said values of voltages and resistances being such that current appliedto said base electrode of said transistor has values integrally relatedto 10 second means for supplying direct current; an ammeter having twoscales reading 0-100 and 0-316, respectively, means, including a currentlimiting resistor connecting said ammeter to said second direct currentsupply means in series circuit; a second plurality of electricalresistance elements; means for selectively connecting any one of saidsecond plurality of resistance elements in parallel circuit with saidammeter; and means for connecting said series circuit and the parallelcircuit to the collector electrode of said transistor; said secondplurality of resistance elements having resistance values selected toprovide different full-scale deflection ranges for collector current, oneach of said plurality of scales, commensurate with the incrementallyvariable current values to which said base current is restricted.

2. The combination according to claim 1 further including a balancecircuit for adjustably reducing the current fiow through said ammeter,said balance circuit including a variable resistance selected to providesaid balance circuit with a much higher impedance than that of theammeter circuit path; and means for selectively connecting said balancecircuit to said ammeter and in parallel circuit with said currentlimiting resistor and said second direct current supply means.

3. The combination according to claim 2 wherein said first plurality ofelectrical resistance elements have values, respectively, of 1.5K, 4.7K,15K, 47K, 150K, 470K, 1.5M, 4.7M, 15M and 47M and wherein said secondplurality of resistance elements have values .047582, .1509, .14759, 7

References Cited Electronic Industries (Sylvan), October 1958, pp. -92.

Radio-Electronics (Bernard), vol. 33, N0. 4, April 1962, pp. 42-44.

WALTER L. CARLSON, Primary Examiner.

E. L. STOLARUN, Assistant Examiner.

1. IN A CIRCUIT FOR MEASURING D.C. AND DYNAMIC CURRENT AMPLIFICATIONFACTOR OF A TRANSISTOR UNDER TEST, AND COLLECTOR-EMITTER CURRENT WITHBASE OPEN, THE COMBINATION COMPRISING MEANS FOR CONNECTING SAIDTRANSISTOR IN COMMON EMITTER OPERATIONAL MODE IN SAID CIRCUIT; FIRSTMEANS FOR SUPPLYING DIRECT CURRENT; A FIRST PLURALITY OF ELECTRICALRESISTANCE ELEMENTS; SWITCH MEANS FOR SELECTIVELY APPLYING CURRENT FROMSAID FIRST DIRECT CURRENT SUPPLY MEANS TO THE BASE ELECTRODE OF SAIDTRANSISTOR VIA ANY ONE OF MORE OF SAID RESISTANCE ELEMENTS TO SUPPLYINCREMENTALLY VARIABLE BASE CURRENT TO SAID TRANSISTOR; SAID FIRST MEANSFOR SUPPLYING DIRECT CURRENT INCLUDING A FIRST CONSTANT VOLTAGE SOURCEAND A SECOND CONSTANT VOLTAGE SOURCE, SAID VOLTAGE SOURCES BEING OF THESAME VOLTAGE VALUES, AND SWITCH MEANS FOR SELECTIVELY CONNECTING ONE OFSAID CONSTANT VOLTAGE SOURCES OR BOTH OF SAID CONSTANT VOLTAGE SOURCESIN SERIES TO PROVIDE SAID CURRENT; SAID FIRST PLURALITY OF RESISTANCEELEMENTS HAVING RESISTANCE VALUES SELECTED TO RESTRICT INCREMENTALVARIATION OF SAID BASE CURRENT TO CURRENT VALUES WITHIN THE SET 10N/2CURRENT UNITS, WHERE N IS AN INTEGER, 0$ N$9; SAID VALUES OF VOLTAGESAND RESISTANCES BEING SUCH THAT CURRENT APPLIED TO SAID BASE ELECTRODEOF SAID TRANSISTOR HAS VALUES INTEGRALLY RELATED TO 10N/2; SECOND MEANSFOR SUPPLYING DIRECT CURRENT; AN AMMETER HAVING TWO SCALES READING 0-100AND 0-316, RESPECTIVELY, MEANS, INCLUDING A CURRENT LIMITING RESISTORCONNECTING SAID AMMETER TO SAID SECOND DIRECT CURRENT SUPPLY MEANS INSERIES CIRCUIT; A SECOND PLURALITY OF ELECTRICAL RESISTANCE ELEMENTS;MEANS FOR SELECTIVELY CONNECTING ANY ONE OF SAID SECOND PLURALITY OFRESISTANCE ELEMENTS IN PARALLEL CIRCUIT WITH SAID AMMETER; AND MEANS FORCONNECTING SAID SERIES CIRCUIT AND THE PARALLEL CIRCUIT TO THE COLLECTORELECTRODE OF SAID TRANSISTOR; SAID SECOND PLURALITY OF RESISTANCEELEMENTS HAVING RESISTANCE VALUES SELECTED TO PROVIDE DIFFERENTFULL-SCALE DEFLECTION RANGES FOR COLLECTOR CURRENT, ON EACH OF SAIDPLURALITY OF SCALES, COMMENSURATE WITH THE INCREMENTALLY VARIABLECURRENT VALUES TO WHICH SAID BASE CURRENT IS RESTRICTED.